Coronary
heart disease (CHD) is the leading cause of death in the
United States and with one exception has been every year
since 1900. CHD is also the most expensive disease in
terms of costs, hospital stays, doctor visits, rehabilitation,
emergency room visits as well as preventative measures.

Women
often fear breast cancer more, but CHD is the number one
cause of death. For women CHD occurs approximately 10
years later than in men but it is often fatal, 67% percent
of the time death is the first symptom. Once a woman reaches
menopause the risk of heart disease and stroke rise dramatically
with age.

BLOOD
LIPIDS

In
October 1999 the FDA approved a new health claim for soy
protein and coronary heart disease. Specifically, the
claim states that “diets low in saturated fat and
cholesterol that include 25 grams of soy protein a day
may reduce the risk of heart disease.” The legislation
authorizing health claims requires significant scientific
evidence and scientific consensus before approving any
claims for foods relative to reducing the risk of a disease.
The agency analyzed the results of nearly 40 clinical
trials before granting the claim.

The
American Heart Association endorses eating soy foods to
lower cholesterol and triglycerides and the risk of heart
disease. Specifically, soy protein preferentially lowers
LDL cholesterol and lowers total cholesterol, two of the
major risk factors in CHD. Moreover, it does not lower
HDL cholesterol as many interventions do.

A
landmark meta-analysis (Anderson, et al.1995) was conducted
that evaluated the affect of soy protein intake on serum
lipids. The study, published in the New England Journal
of Medicine, analyzed the results of 38 controlled clinical
trials. The results showed that ingestion of soy protein
was associated with significant declines in total cholesterol,
LDL cholesterol and triglycerides.

It’s
important to note the results of these studies. The Anderson
study focused on soy protein and the FDA claim for heart
health is specifically for soy protein. The Zhuo study
concluded that isoflavones have LDL cholesterol-lowering
effects independent of soy protein. This means that consumers
who need to lower their risk for heart disease are likely
best served by foods or supplements that contain both
soy protein and isoflavones versus isoflavone supplements
alone. However, FDA recognizes only soy protein for its
approved health claim.

Consumption
of soy protein does not appear to have a hypocholesterolemic
effect in adults with low or normal cholesterol levels.
There is no evidence to suggest that soy consumption could
cause dangerously low levels of cholesterol.

Nestel
et al. (1997) performed a placebo-controlled, crossover
trial using isoflavone tablets (80 mg isoflavone of which
45 mg was genistein) and placebo tablets in which systemic
arterial compliance was measured within the main conduit
arteries. Isoflavones significantly improved systemic
arterial compliance. The placebo had no effect on systemic
arterial compliance while the isoflavone group experienced
a 26% improvement. The authors speculated that the smooth
muscle layer within the vessel wall may be influenced
by endothelial cell events and that soy isoflavones stimulate
endothelial-related arteriolar relaxation.

In
a trial (Steinberg et al., 2003) designed to evaluate
the effect of isolated soy protein compared to caseinate
on plasma lipoproteins and endothelial function in postmenopausal
women soy protein was shown to significantly (P < 0.05)
increase flow-mediated dilation compared to baseline (9.4
± 1.8% versus 5.3 ± 1.2%) and compared to
caseinate (9.4 ± 1.8% vs. 4.9 ± 1.5%). In
a second study 28 women were enrolled in a randomized,
double-blind, crossover study and they consumed 25 grams
of 3 protein products/day for 6 weeks each with intervening
washout periods (Cuevas et al., 2003). The products were
isolated soy protein with isoflavones, ethanol-washed
isolated soy protein with trace isoflavones, and total
milk protein. The results indicated that the postocclusion
peak flow velocity of the brachial artery was significantly
(P = 0.03) lower after treatment with isolated soy protein
with isoflavones than after treatment with total milk
protein. This result is consistent with a vasodilatory
response.

Other
studies have reported beneficial effects of soy or soy
isoflavones on LDL particle size (Deroches et al., 2004)
and homocysteine levels (Nagata et al., 2003). In a study
conducted among 36 moderately hypercholesterolemic men
and women consumption of soy protein was associated with
a larger LDL peak particle size relative to animal protein
(Desroches et al., 2004). The shift in LDL particle size
represents a less atherogenic pattern. This effect was
associated with soy protein and was independent of the
isoflavone component. Elevated blood homocysteine levels
are an independent risk factor for cardiovascular disease
and a recent cross-sectional study of the relationship
between soy intake and homocysteine levels indicated that
increased soy intake was associated with lower blood homocysteine
levels (Nagata et al., 2003).

While
a number of these areas clearly require more investigation
there is growing evidence that soy has significant positive
effects on cardiovascular health. It’s possible
to argue that although the improvements in lipid profiles,
while important, may not be the benefit of greatest value.